The objective of this research is to study the pathogenic ability of the bacterium Haemophilus parainfluenzae. H. parainfluenzae is frequently isolated from the sites of respiratory disease in humans, however, little direct evidence exists that demonstrate that the bacterium causes damage to the host tissue. This study proposes an investigation of the ability of H. parainfluenzae strains to bind to and invade human respiratory epithelium and to cause inflammation by the epithelial tissue. Evidence that H. parainfluenzae can adhere to epithelium and elicit an inflammatory response would support the hypothesis that the bacterium is an opportunistic pathogen of compromised respiratory tissue. Additional studies will be performed to establish profiles about the lipooligosaccharide, outer membrane proteins, and fimbriae of all strains studied. This information sheds light on the degree of surface variation in the species and also may help to predict molecules involved in adherence to human cells. Finally, the ability of H. parainfluenzae to form biofilms will be determined. Production of biofilms has been shown to be beneficial for pathogens of the human respiratory tract. By completing these studies, we hope to gain a better understanding of the basic molecular biology of the bacterium H. parainfluenzae and as well as determining if the bacterium possesses the abilities. [unreadable] [unreadable] [unreadable] [unreadable]